The invention relates to a flexible line guide for an industrial robot according to the introduction to claim 1.
Such guides are commonly used for carrying an outer line in the form of a welding cable or a pressurised fluid line, for example, between the foot and the rotating upper section of an industrial robot.
Guides of this type are known, for example, from U.S. Pat. No. 5,694,813 and EP-A-0 552 688. A disadvantage of such known guides is that the outer peripheral side of the loop, especially at the bend, must be guided by the inside of a stationary cylindrical wall or a cylindrical wall that rotates together upper section of the robot, in order not to deviate outwards from the path of movement around the axis, which causes undesirable friction and wear on the covering of the line.
One objective of the present invention is to achieve a guide of the type stated in the introduction that significantly reduces wear and thus increases the working life of the covering of the line.
A second objective is to obtain a guide that makes it easy to replace the line.
These are achieved by means of the features that are stated in the following claims.
According to an aspect of the invention, a separate groove for every strand is the only engagement provided between the cable loop and the parts that rotate relative to one another. In this way, none of the strands nor the bend come into sliding contact with a wall, as is the case in the prior art, so that essentially all the relative movement between the covering of the line and the parts that rotate relative to one another that causes wear is eliminated. A further advantage with this arrangement is that thanks to the resulting free space between the grooves, the line is easier to remove from the guide and be put back there when it needs to be replaced.
According to one preferred embodiment of the invention, the grooves have different mutual radii so that the bend will be angled relative to the common axis of rotation. In this way, the radius of curvature of the bend can also be increased advantageously at a pre-determined axial distance between the grooves. This ensures partly that the insignificant relative movement that does nevertheless occur between the line and the groove takes place primarily only at the transition between the strand and the bend of the groove with the smaller radius and partly that the bend has less of a tendency to deviate at a tangent outwards from the path of rotation since it leans inwards from the largest radius.
If the grooves are formed in groove elements that can be mounted on the outsides of the respective parts in a removable fashion, an existing robot can later easily have an additional guide fitted according to the invention.
Other features and advantages of the invention are evident from the claims and the following detailed description.